A complex event processing (CEP) is a process for extracting only a meaningful event from events occurring in real time to perform corresponding actions. During a stream data processing of data, the input data is processed in a memory without being recorded in a hard disk drive (HDD) so that the data may be processed at a high speed. Further, it is not necessary to process all the data because data processed immediately before is kept as intermediate data and a difference between the data which flows into the memory and the intermediate data is the amount of data which needs to be processed.
During such a complex event processing, a real-time property is important, so that an in-memory processing manner is used. In the complex event processing, scalability is supported in a scale-out and scale-up manner as in a distributed processing system. The scale-up manner is a manner which increases a performance of a computing device which performs the complex event processing and the scale-out manner is a manner which improves a processing ability by increasing the number of computing devices which perform the complex event processing.
When the scalability extends by the scale-out manner, a cost for extending is cheaper than that of the scale-up manner and a possibility of overall failure is low. In contrast, when the scalability extends by the scale-out manner, data consistency needs to be maintained.